The traditional refrigerants applied to domestic refrigeration until the mid-nineties were compounds based on chlorofluorocarbon (CFCs). However, since these compounds have proved to cause damages to the ozone layer in the high atmosphere, the use of such compounds is now limited and regulated under the terms of the Montreal Protocol. The CFCs used in domestic applications were initially substituted by hydrofluorocarbons (HFCs) which have zero potential of aggression to the ozone layer (ODP). Nevertheless, the application of HFCs compounds has a significant global warming potential (GWP), and for this reason said HFCs compounds have been substituted by hydrocarbons (HC)-based refrigerants, mainly in European and Asian domestic markets.
The change of refrigerants in refrigeration systems also leads to a change in the lubricant oils used in these refrigeration system, due to the necessity of making said components mutually compatible in the compressor of said refrigeration systems, in order to avoid, for example, reactions that produce acids in these systems and other components that are prejudicial to the integrity and efficiency of said system.
For systems using HFC refrigerants there are known some prior art solutions that utilize the alkylbenzene lubricant oil, as described in U.S. Pat. No. 6,207,071 (in which said oil is used with or without phosphoric esters-based additives in specific ratio and molecular weight). Said solution disclosed in U.S. Pat. No. 6,207,071 requires, to be utilized with the refrigerants consisting of HFC-134a and/or HFC-125, a lubricant oil comprising an alkylbenzene oil containing 60% by weight of alkylbenzene oil with molecular weight of 200-350 and, in case of using additives, 0.01-5.0% by weight (based on the total amount of the present oil composition) of a phosphoric ester compound.
Although this lubricant oil solution presents advantages in its use as a lubricant in refrigeration systems containing HFC, such composition is not applicable in temperature conditions inferior to about 20° C., since the present lubricant oil presents, in these or in lower temperatures, a low miscibility with the refrigerants consisting of HFC-134a and/or HFC-125. At temperatures around 0° C. or lower, this known prior art lubricant oil cannot be applied with refrigerants consisting of HFC-134a and/or HFC-125.